Elektronische Orgel

摘要

1,187,579. Electrophonic musical instruments. WURLITZER CO. 25 March, 1969 [24 April, 1968], No. 15584/69. Heading G5J. An electronic organ comprises a number of tone generators 32 producing oscillations -of predominantly one polarity, and a number of keys each operating a key switch 34, said switches being connected to an output circuit which includes at least one capacitor connected so as to be charged with the one polarity upon closure of one -of the key switches -and a biasing potential source of the one polarity e.g. + 0À85V over line 118 connected to the output circuit to maintain the capacitor at least partially charged with the one polarity when all the key switches are open. Square waves are used varying between zero and a positive value (Fig. 6, not shown) and the biasing potential, approximately equal to the average potential of the square wave, is connected to the collector viz. bus-bars 46, of the switches thus reducing the "key-plop" caused by the closing of a key switch, the "key-plop" is further reduced by incorporating the capacitor in a low frequency roll-off filter (Fig. 7, not shown). If a square wave were used that varied between two fixed D.C. voltages other than zero, the biasing potential applied to each bus-bar would be the average of these two voltages. An 81 flute stop is shown, each generator 32 being connected to a movable switch contact 44 which engages a busbar 46 upon depression of the corresponding key. Nine switch contacts 44 are engageable with the bus-bar 46-1 while eight switch contacts are engageable with each of the remaining five busbars. Each bar is connected to a different filter, and the outputs of these filters may be selectively combined, the combined outputs being connected to further filters. Substantially all the harmonics are filtered out by means of a high frequency roll-off filter (Fig. 8, not shown). Most of the "key-plop" is caused by the charging of primarily the capacitors 48, 50, 56 and possibly 60 and thus each bus-bar is supplied with a positive potential + 0À85V. A second output is taken from each bus-bar and combined with the output from a 41 flute stop to produce a sawtooth wave for subsequently producing reed, string and brass tones. A mixture amplifier and switching including four .generators 2 2/31, 21, 1 3/51 and 11 stops is also described (Fig. 4, not shown). The tone generators are connected in parallel to complex filters and to flute filters, and the respective filter outputs are selectively combined and connected to an amplifier (40, Fig. 5, not shown) connected to a power amplifier and loud speaker system.